How to install a roof-mounted RV solar kit, step by step

Before you start

This guide assumes you've already sized your system (Planning an RV solar system for Alberta: energy audit, panels, batteries and controller) and chosen a wiring layout (Wiring RV solar panels in series, parallel or series-parallel). Read every manual that came with your kit. Where this guide and your manual differ, follow the manual.

Safety: Roof work is a fall hazard. Use a sturdy ladder, confirm with your RV manufacturer that the roof is walkable (and where), and never work on a wet, frosty or windy roof. Solar panels produce voltage whenever light hits them. Keep panels covered with an opaque blanket or cardboard while you wire, and never connect or disconnect MC4 connectors under load. Batteries can deliver enough current to weld tools and start fires. Remove rings and watches, and use insulated tools.

What you'll need

• Solar kit: panels, mounts, MC4 cables and charge controller
• Roof cable entry gland and self-leveling lap sealant compatible with your roof membrane
• UV-rated PV wire long enough for your route
• A DC breaker or disconnect for the PV input and a fuse or breaker on the controller output
• Cable, lugs and a ratcheting crimper sized for your currents
• A multimeter, drill, sealant scraper and cleaning supplies for the roof

Step 1: Plan the layout

1. Measure the roof and mark the A/C, vents, antenna, skylights and the paths you need for walking and maintenance.
2. Place panels where they won't be shaded by the A/C or other equipment. Even partial shade on one panel can cut output a lot, especially in series strings.
3. Leave room around panels to reach and reseal other roof fixtures later.
4. Decide where the cable comes into the RV. Common choices are the fridge vent (if the manufacturer allows it), a cabinet near the battery, or an existing plumbing vent area. Never route cables through a propane appliance's combustion or exhaust path.

Step 2: Confirm what you're screwing into

RV roofs vary: rubber (EPDM), TPO, fibreglass or aluminium over wood or laminated foam. Screws need solid backing such as roof rafters or plywood decking. Your RV manufacturer may publish rafter locations or approved mounting methods. Some kits use VHB adhesive tape in addition to or instead of screws. Use the method the panel kit and RV manufacturer approve.

Step 3: Mount the panels

1. Clean the roof where mounts will sit, using a cleaner safe for your membrane.
2. Attach mounts (Z-brackets or feet) to the panels on the ground first.
3. Lift the panels onto the roof safely. Get a helper.
4. Position each panel, mark the mount holes and pre-drill as the instructions say.
5. Bed each mount in sealant or butyl if specified, then fasten it.
6. Cover every screw head and mount edge with lap sealant, feathering the edges.

Leave an air gap under the panels. Panels produce less power when hot, and the gap also helps snow and water shed.

Step 4: Wire the panels on the roof

Connect the panels in series, parallel or series-parallel according to your plan, using MC4 connectors (or branch connectors and a combiner where needed). Keep the panels covered while you work.

Secure cables with UV-rated clips or ties so they can't flap or rub on the roof. Leave a drip loop before the cable entry.

Step 5: Install the roof cable entry

1. Drill the hole for the gland, staying clear of framing and wiring below.
2. Feed the cables through, mount the gland in sealant, and fasten it.
3. Cover the flange edges and screw heads with lap sealant.

Alberta: Hail and big temperature swings are hard on roof sealant. Inspect the panel mounts and cable entry with the rest of your roof every spring and fall. RV roof maintenance and resealing: a practical inspection and resealing routine covers what to look for.

Step 6: Mount the charge controller near the battery

Mount the controller on a non-flammable surface in a ventilated spot, as close to the battery as practical. The controller-to-battery cable carries the full charging current, so a short run keeps voltage drop low. Follow the manual's clearance and mounting-orientation requirements. Don't mount it inside a sealed compartment with flooded lead-acid batteries, since they can vent explosive gas.

Step 7: Add protection

• A DC breaker or disconnect between the array and controller lets you isolate the panels safely.
• A fuse or breaker on the controller's battery side, close to the battery or bus bar, sized per the controller manual and the wire.
• Fuses on parallel strings where required (see Wiring RV solar panels in series, parallel or series-parallel).

Details are in RV solar and battery fusing, breakers, grounding and safety.

Step 8: Connect in the right order

Most charge controller manuals say to connect the battery first, then the solar array, so the controller can detect system voltage. Disconnect in the reverse order: array first, then battery. Check your manual and follow its order exactly.

1. With all breakers off and fuses out, connect the controller to the battery (through its fuse or breaker).
2. Close the battery-side fuse or breaker. The controller should power up.
3. Set the battery type and charging profile.
4. Uncover the panels, measure PV voltage at the controller input with a multimeter and confirm the polarity is correct.
5. Close the PV breaker.

Step 9: Test and commission

• In good sun, confirm that the controller shows PV voltage, charging current and charging stage.
• Check that all connections are tight and cool to the touch after an hour of charging.
• Watch the battery monitor over a few days to confirm the system keeps up with your usage.
• Label breakers and fuses.

When to call a pro

Get help if you're not sure about roof structure, if you need to tie into an existing converter, alternator or lithium system, or if any part of the project touches the 120V AC system. That should be done by a licensed electrician.

Related guides

• Planning an RV solar system for Alberta: energy audit, panels, batteries and controller
• RV solar and battery fusing, breakers, grounding and safety
• RV solar not charging: how to troubleshoot panels, controller and wiring
• RV roof leak: how to find the source and fix it properly